1. Field of the Invention
The present invention relates to wireless communication systems, and more particularly, to a collinear antenna array for a portable wireless communication device that permits enhanced system performance by increasing antenna gain without exceeding radiated power requirements.
2. Description of Related Art
Portable wireless communications systems are increasingly prevalent in the art as a convenient way to permit remote elements of a system to operate together. A particularly useful application of wireless communication is that of a wireless local area network (WLAN) in which a plurality of remote computing devices communicate together using radio frequency (RF) signals. The remote computing devices include a radio transceiver adapted for RF communication with each other as well as with the other elements of the WLAN. The WLAN may also include a central host processing unit, or network master, that sends information to and receives information from any one of the plurality of remotely disposed computing devices. Such WLAN systems offer increased flexibility over conventional wired LAN systems by enabling operators of the remote computing devices substantial freedom of movement through the environment, and may be found in diverse data collection applications such as inventory control, manufacturing and production flow management, and asset tracking.
A significant drawback of wireless communication systems is their limited range due in part to compliance with governmental communication regulations. In order to prevent interference between competing communications systems operating in the same general vicinity, governmental regulatory agencies limit the maximum amount of transmitted power from an RF transceiver. The limit in transmitted power tends to limit the operational range of the communication systems, which impairs the overall usefulness of the wireless communication system.
Currently, there are two methods under which regulatory agencies specify the maximum allowable output power. A first type of regulation specifies the maximum power (dBm/Hz of bandwidth) that can be sent from the transceiver to the antenna and/or to restrict the amount of gain that may be provided by the antenna. A second type of regulation specifies a maximum radiated power level measured at a predetermined distance from the transceiver. The European Telecommunications Standards Institute (ETSI) has adopted regulations under this second type of regulation. According to the ETSI regulations, for example, a maximum radiated power level of 20 dBm (100 mW) is permitted, and gain antennas may not be used to bring the signal level above the radiated power limit.
Thus, it would be highly desirable to provide a wireless communication system having a greater operational range without exceeding radiating power regulations.